Originally Posted by seafan
BillyZ the Idea of the displacement of water causing the sound is not really feasible, although gas is easily displaced and compressed, water is very difficult to compress. The idea that a shrimp can move fast enough to create a vacuum in an extremely viscous fluid is hard to believe. If this is not what you meant please explain.
P.S If that were true, the displacement caused by a tsunami would sound like thunder, and could be heard miles away.
P.P.S Test it... Take a capped bottle completely filled with water and put it under pressure, or take it into an airplane, and then do the same to one filled with air, see if the one filled with water changes shape.
Actually, you can NOT compress water at all. Thats what makes the theory of hydraulics work. It can be under pressure, but not compressed. Waters inability to be compressed has no bearing on the creation of a vacuum. A vacuum is a complete lack of any substance
. The shrimp's claws create this through momentum. The water between the club and the crab is forced away at such a high velocity that it's momentum continues to cary it away from the point of impact in all directions, thus creating the vacuum.
I don't follow your counterpoint on the tsunami. The displacement created by a tsunami is not a vacuum, that is a slow receding as the wave mass builds.
And you're right, the fact that a little shrimp can hit something fast enough and hard enough to create a vacuum under water is hard to believe, but it is what is happening. Animals do a lot of hard to believe things.